National Journal of Physiology, Pharmacy and Pharmacology RESEARCH ARTICLE
Effects of overnight sleep deprivation on autonomic function and perceived stress in young health professionals and their reversal through yogic relaxation (Shavasana) Raghul S1, Vasanthan S2, Ananda Balayogi Bhavanani3, Jaiganesh K2, Madanmohan T2 II MBBS Student, Mahatma Gandhi Medical College and Research Institute, Puducherry, India, 2Department of Physiology, Mahatma Gandhi Medical College and Research Institute, Sri Balaji Vidyapeeth, Puducherry, India, 3Center for Yoga Therapy Education and Research, Sri Balaji Vidyapeeth, Puducherry, India 1
Correspondence to: Vasanthan S, E-mail:
[email protected]
Received: April 25, 2018; Accepted: May 03, 2018 ABSTRACT Background: Extensive research has been done to demystify the effects of sleep deprivation on cognitive functions, memory, and reasoning ability. However, there is a lacuna in regard to the effects on autonomic function and perceived stress as well as its modulation through yogic relaxation. Healthcare professionals often work at night, and the effect of acute overnight sleep deprivation on their performance is crucial. Aims and Objectives: The present study was undertaken to study the effects of overnight sleep deprivation on autonomic function and perceived stress in health-care professionals and to determine its modulation through yogic relaxation (Shavasana). Materials and Methods: A total of 35 healthcare professionals, aged between 20 and 25 years, were recruited from emergency services wing (casualty) of MGMC and RI, Puducherry, and taught yogic relaxation. Heart rate (HR), blood pressure (BP), and HR variability (HRV) were recorded and Cohen’s perceived stress scale (PSS) administered before the commencement of day duty. Parameters were again recorded after overnight sleep deprivation due to night shift work and then after they practiced yogic relaxation (Shavasana). As data passed normality testing, Student’s paired t-test was used to compare the changes after sleep deprivation and then after yogic relaxation. Results: Overnight sleep deprivation resulted in statistically significant (P < 0.05) increases in systolic BP (SBP), low frequency (LF), LF/high frequency (HF), diastolic BP (DBP), PSS, and mean HR. This was coupled with significant decreases in mean RR, SDNN, pNN50, HF, and RMSSD. Following yogic relaxation, these changes were reversed, and significant decreases were witnessed in LF, LF/ HF, SBP, mean HR, DBP, and PSS with significant increases in mean RR, pNN50, HF, RMSSD, and SDNN. Conclusion: The findings of our study reiterate the negative effects of sleep deprivation on cardiac autonomic status. Such deleterious effects may be partially reversed by practicing yogic relaxation (Shavasana). Such conscious relaxation may be able to help correct imbalance of autonomic nervous system by enhancing parasympathetic tone and reducing sympathetic overactivity. KEY WORDS: Overnight Sleep Deprivation; Heart Rate Variability; Perceived Stress Scale; Yogic Relaxation; Shavasana Access this article online Website: www.njppp.com
DOI: 10.5455/njppp.2018.8.0415003052018
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INTRODUCTION A person’s quality of life can be disrupted due to many different reasons, and one important yet underestimated cause for that is sleep loss.[1] Professions such as health care, security, and transportation often require working at night, and the deleterious effect of acute overnight sleep
National Journal of Physiology, Pharmacy and Pharmacology Online 2018. © 2018 Vasanthan S, et al. This is an Open Access article distributed under the terms of the Creative Commons Attribution 4.0 International License (http://creative commons.org/licenses/by/4.0/), allowing third parties to copy and redistribute the material in any medium or format and to remix, transform, and build upon the material for any purpose, even commercially, provided the original work is properly cited and states its license.
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Sleep deprivation on autonomic function and perceived stress and reversal by Shavasana
deprivation on performance is crucial. Increased blood pressure (BP), heart rate (HR), and urine catecholamine levels have been associated with acute sleep deprivation, and it has been linked to potentially serious changes to emotion, mood states, and their regulation.[2-4] It has been reported that sleep deprivation increased subjective stress, anxiety, and anger ratings with elevated negative mood by lowering the psychological threshold for the perception of stress.[5] It is also well known that sleep deprivation may increase the incidence of cardiovascular events, with a high incidence of sudden death, myocardial infarction, and stroke in the early morning attributed to sympathetic overstimulation.[6-9] Although extensive research has been done to demystify the effect of sleep deprivation on cognitive functions, memory, and reasoning ability, there is a lacuna in its effects on autonomic function and perceived stress as well as the modulation of such responses to yoga. Yoga is the best lifestyle ever designed and is increasing in popularity worldwide with a recent report suggesting that 15 million Americans have practiced yoga at least once in their lifetime.[10] Yoga facilitates psychosomatic relaxation, and earlier studies have shown that Shavasana and Savitri pranayama in trained subjects cause a significant decrease in oxygen consumption, HR, and diastolic BP (DBP) while Shavasana alone has been shown to be effective in the treatment of hypertension.[11-13] It is also known that sleep duration in long-term experienced meditators is lower than in non-meditators and general population norms, with no apparent decrements in vigilance.[3] HR variability (HRV) is non-invasive and well-established physiological parameter used to assess sympathovagal balance, an index of cardiac autonomic function.[14] Increase in HRV is associated with decreased sympathetic and increased vagal tone influence on the sinoatrial SA node of heart while decreased HRV and sympathovagal balance have been reported to be associated with cardiovascular morbidity and mortalities.[15,16] Yogic relaxation (Shavasana) is known to induce psychosomatic relaxation and enhance one’s ability to combat stress.[11,12] However, to the best of our knowledge, no study has been done to determine the effectiveness of yogic relaxation (Shavasana) of short duration on physiological functions, especially on mitigating the effect of overnight sleep deprivation. With the above background in mind, the present study was designed with the following aims and objectives: 1. To study the effect of overnight sleep deprivation on autonomic function test and perceived stress in young healthy volunteers. 2. To provide evidence for the same through: a. HRV measures (time and frequency domain),
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b. HR and resting BP (systolic BP (SBP) and diastolic DBP), and c. Perceived stress scale (PSS). 3. To compare the differential effect of overnight sleep deprivation and normal sleep on the above-mentioned parameters. 4. To study the effect of Shavasana on overnight sleepdeprived subjects. MATERIALS AND METHODS Before commencement of the study, the Institute Research Committee (IRC) and IHEC approval were obtained. A total number of 35 healthcare professionals in the age group between 20 and 25 years were recruited from casualty and ICU unit of Mahatma Gandhi Medical College and Research Institute, Puducherry. All parameters were recorded in the Research Laboratory of the Department of Physiology, MGMCRI. Subjects were explained about the method of recording and were familiarized with the laboratory environment. Recordings were obtained between 8 and 10 am without any stimulants in pre-recording period. The laboratory temperature was maintained at a comfortable level with subdued lighting. Basal recordings were done before the commencement of day duty. In the same subjects, all parameters were again recorded after overnight sleep deprivation due to night shift work. Yogic relaxation (Shavasana) was performed by the subjects on the day after overnight duty and parameters recorded post-relaxation phase. Technique of Yogic Relaxation (Shavasana)[12] The subjects were asked to lie down in a calm and quiet room in the supine position with the hands and legs fully extended. The feet were kept side by side with the toes directed outwards. The arms were kept close to the body at an angle of approximately 15 with the trunk, keeping the forearms in mid prone position and fingers relaxed. The eyes were closed lightly, and the subjects were asked to perform slow rhythmic breathing. They were instructed to keep their attention to the sensation of breathing at the nostrils only. The devitalization of group of muscles was carried out in the following order: First, the lower limbs, then the upper limbs, neck, face, and finally, the trunk. During this, the subjects were suggested to feel that a particular group of muscle is completely relaxed and has become non-impressional to both the afferent and efferent stimuli. The subjects were asked to retain this posture for about 30 min, after which the revitalization is done in the same order in which the muscles were devitalized. Then, they were asked to sit up for a minute before standing. Recording of HRV Subjects were asked to relax in a supine position on the couch and allowed to relax for 10 min. Lead II ECG and
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Sleep deprivation on autonomic function and perceived stress and reversal by Shavasana
respiration were recorded at the 500 samples per sec using INCO Polyrite-D for 5 min. R-R interval data were extracted by RMS Polyrite software, and then, HRV was analyzed from R-R interval by Kubios HRV, version 2.0, Department of Physics, University of Kuopio, Finland. HRV data analysis and signal processing followed guidelines defined by “Task Force of the European Society of Cardiology and the North American Society of Pacing and Electrophysiology” Time domain components are mean HR, mean RR, standard deviation of RR intervals SDNN, square root of the mean of the sum of the squares of differences between adjacent RR intervals RMSSD, adjacent RR interval differing more than 50 ms (NN50), and NN50 counts divided by all the RR intervals (pNN50). Frequency domain components consisted of very lowfrequency (VLF) component (0.003–0.04 Hz), LF component (0.04–0.15 Hz), and high-frequency (HF) component (0.15–0.5 Hz) and LF/HF ratio; the ratio of LF power to HF power, LF power in normalized units (LF nu) = (LF × 100)/ (TP-VLF), and similarly HF nu was calculated. HF, HF nu, SDNN, RMSSD, NN50, and pNN50 reflect cardiovagal tone; LF reflects both the sympathetic and parasympathetic tones; VLF component’s interpretation is not clear, and it cannot be interpreted using short-term HRV recordings; LF nu and HF nu represent a relative tone of sympathetic and parasympathetic nervous system PSNS. Recording of BP After 15 min of rest in supine, SBP and DBP were obtained from the subjects using sphygmomanometer. The average of three trials with 5 min interval was taken for calculation. Cohen’s PSS Questionnaire It is most widely used psychological questionnaire for subjects’ perception of stress. A 10-item Cohen’s PSS questionnaire was used to score feeling and thoughts during last month in this study. All the questions were explained to the subjects and requested to answer. PSS scores were obtained by reversing responses (e.g., 0 = 4, 1 = 3, 2 = 2, 3 = 1, and 4 = 0) to the four positively stated items (items 4, 5, 7, and 8) and then summing across all scale items. A short 4-item scale is made from questions 2, 4, 5, and 10 of the PSS 10-item scale. Statistical Analysis After obtaining the study data, it was statistically analyzed using SPSS version 16.0. All data passed normality testing by Kolmogorov–Smirnov Test, and then, Students paired t-test was used to compare the differences in the subjects before and after the relaxation. 3
RESULTS The results are given in Tables 1 and 2. Comparison of BP, PSS, and HRV recordings before day duty and post night duty revealed significant increases in SBP, LF, and LF/HF (P < 0.05) and DBP, PSS, and mean HR (P < 0.01), with Table 1: Comparison of BP, PSS, and HRV parameters recorded before day duty and post night duty in 35 young healthcare professionals Parameters
Before day duty
Post night duty
SBP (mmHg)
112.16±7.22
116.16±7.48*
DBP (mmHg)
75.44±8.48
79.38±7.36***
PSS
18.30±3.44
20.36±3.76***
Mean HR
73.88±3.85
76.13±4.65**
Mean RR
874.24±115.43
841.91±106.3*
SDNN
56.31±8.51
49.47±9.46*
RMSSD
53.43±12.70
45.32±13.66**
pNN50
26.62±8.50
21.20±4.57*
LF (ms2)
495.54±59.28
522.62±44.15*
HF (ms2)
214.07±43.23
165.94±60.28*
2.31±0.45
3.14±0.32*
LF/HF
Values are given as mean±SD. *P
